Ok, I'm on the PGCE so it might be different to the undergrad but I'll give you some tips. They are looking for people who really know what the are getting into, so be aware of the long hours planning and marking not just the fun classroom stuff. Have an opinion an some educational matters at the moment, like teachers working hours, pensions, constant changes to the curriculum. They might ask what do you think makes a good teacher so think about that (you can even google that for some ideas!). They may ask about a teacher that inspired you or why do you want to teach. Like I said, they want someone who knows how challenging it is, that you have thought it through and you can cope with the course. They aren't expecting you to know everything already as that's why you need to do the course in the first place. Just that you know what's involved and that you have a genuine care and interest in children. If you have any relevant experience with children make sure you drop that in as often as you can, bring your own experiences into it.
Hope that helps